Lecture 4 - Anaphylaxis Flashcards
What is the definition of anaphylaxis?
- A serious, life-threatening generalized or systemic hypersensitivity reactions
- A serious allergic reaction that is rapid in onset and might cause death
What is the pathophysiology of anaphylaxis?
- An acute systemic, allergic reaction
- During an initial exposure, individual will form IgE antibodies
- Subsequently, when the individual is exposed to the antigen, it will bind to IgE antibodies => release of vasoactive and inflammatory mediators from mast cells and basophils
- May cause urticaria, angioedema, bronchospasm, hypotension, and GI symptoms
How long do it generally take for anaphylaxis signs and symptoms to occur after exposure?
30 minutes, but can be several hours
What are the 3 categories of anaphylaxis?
1) Immunologic (IgE-mediated or non-IgE-mediated)
2) Nonimmunologic
3) Idiopathic
What is the clinical criteria for anaphylaxis?
- Any one of the three
1) Acute onset of an illness (minutes to hours) w/ the involvement of the skin, mucosal tissue, or both AND respiratory compromise and/or reduced BP or associated symptoms of end-organ dysfunction
2) 2 or more of the following occur rapidly after exposure to a likely allergen - involvement of skin/mucosal tissue, respiratory compromise, reduced BP, persistent GI symptoms
3) Reduced BP after exposure to known allergen
What are the 3 different potential patterns of anaphylactic reactions?
1) Uniphasic
2) Biphasic
3) Protracted
What is a uniphasic anaphylactic reaction?
- Isolated reaction w/ signs and symptoms usually appearing w/in 30 minutes of exposure to allergen
- Spontaneously settles or resolves w/ treatment, generally w/in 1-2 hours
What is a biphasic anaphylactic reaction?
- Anaphylaxis reaction resolves, then symptoms begin again usually w/in 8 hours of first symptoms
- Occurs in up to 20% of patients experiencing anaphylaxis
What is a protracted anaphylactic reaction?
Severe reaction that lasts for an extended time (24-32 hours)
What are the signs and symptoms of anaphylaxis?
- Cutaneous - hives, severe itching, flushing/redness of skin, swelling
- Respiratory - throat or chest tightness, difficulty breathing, wheeze, cough, swelling of tongue, itching of throat
- GI - difficulty or pain swallowing, nausea or vomiting, diarrhea
- CV - hypotension, chest pain, dysrhythmias
- Other reactions - lightheadedness, dizziness, sweating, sudden behavioural changes
What are common triggers of anaphylaxis?
- Foods - peanuts, tree nut, shellfish, milk, eggs
- Drugs - antibiotics, NSAIDs, biologics
- Insect stings - honeybees, yellow jackets, hornets, wasps, fire ants
- Latex
What is the initial treatment for anaphylaxis in the community setting?
- CPR if breathing is affected
- Epinephrine injected immediately; repeat in 10 minutes if needed
- Call 911
What is the mechanism of action for epinephrine autoinjectors?
Act on alpha and beta-adrenergic receptors, leading to restoration of respiratory and CV function by relaxation of bronchial smooth muscle and vasoconstriction to reverse hypotension and stimulate the heart
What is the recommended administration of epinephrine autoinjectors?
Intramuscularly in the mid to outer thigh
What are the various delivery systems for an epinephrine autoinjector?
- EpiPen
- Allerject (not currently available and unknown if it will become available)
- Twinject (discontinued)
- Generics
Epinephrine autoinjectors are a schedule __ medication
2
What is the adult dose of EpiPen?
0.3 mg/dose
What is the child dose of EpiPen?
0.15 mg/dose (15-30 kg)
Are there any contraindications to using epinephrine for allergic reactions?
No
What are the common adverse effects of epinephrine?
- Anxiety
- Tremors
- Pallor (pale appearance)
- Tachycardia
How long after injection of epinephrine should patients feel relief?
5-10 minutes
What is urticaria (hives)?
- Typical lesion is intensely pruritic, erythematous plaque
- May be accompanied by angioedema
What is acute urticaria?
Present for less than 6 weeks
What is chronic urticaria?
Recurrent w/ signs and symptoms recurring most days of the week for 6 weeks or longer
What is the typical appearance of urticaria?
- Smooth, slightly elevated, discoloured area on the body surface, often accompanied w/ severe itching
- May be round or oval and vary in size
- Symptoms often seem most severe at night
What is the pathphysiology of urticaria?
Cutaneous mast cells and basophils in the superficial dermis release multiple mediators upon activation, including histamine, which cause itching and vasodilatory mediators, which cause localized swelling in the uppermost layers of skin
What causes urticaria?
- Allergic reaction to foods, medicines, insect bites, animals, pollen, or latex
- Infections
- Illnesses
- Exposure to sun, heat, cold, or water
- Exercise
- Stress
- Contact w/ chemicals
- Scratching the skin
What is the recommended treatment for acute urticaria?
2nd generation H1 antihistamines
When would you refer a patient with urticaria?
Suspected cases of anaphylaxis to emergency care immediately
What can pharmacists prescribe for urticaria?
Same as for contact dermatitis
What are the goals of treatment for insect bites and stings?
- Prevent stings and bites
- Prevent disease or reactions caused by stings or bites
- Provide symptomatic relief for localized reactions
When would you refer an insect bite or sting?
More severe reactions
What is the general treatment for insect bites and stings?
- Remove insect/stinger
- Apply ice pack to reduce swelling
- Clean area well (warm water to relieve pain and inflammation; cool water to relieve itching)
- Non-prescription oral antihistamines to relieve itching
- Non-prescription topical steroid to relieve inflammation and itching
What are OTC treatment options for insect bites and stings?
- Topical corticosteroids (hydrocortisone 0.5% or 1%)
- Oral antihistamines (diphenhydramine or loratidine)
- Skin protectants (calamine, zinc oxide)
- Topical anesthetics (benzocaine, lidocaine, pramoxine)
- Topical antihistamines (topical diphenhydramine)
- Topical counterirritants (camphor, menthol, ammonia)
What is the method of action for camphor or menthol in treatment of insect bites and stings?
Depress cutaneous receptors resulting in relief of itching and irritation due to anesthetic effect
What is the method of action of topical ammonia in treatment of insect bites and stings?
- Relieves itching and burning due to mosquito bites
- Product - AfterBite (ammonia and baking soda in Original Formula)
What is the method of action of topical anesthetics in treatment of insect bites and stings?
- Cause a reversible blockade of conduction nerve impulses where applied that results in loss of sensation
- Short duration of action
- Risk of hypersensitivity reaction and systemic absorption/toxicity
What is the method of action for topical antihistamines?
Cause an anesthetic effect by depressing cutaneous receptors to relieve pain and itching
What are some side effects to topical antihistamines?
- Allergic contact dermatitis and sensitization
- Generally not absorbed enough to cause systemic side effects, but have shown anticholinergic toxicity with excessive use in children
What is the method of action of skin protectants?
- Reduce inflammation and irritation
- Absorb fluids from weeping lesions
What are some oral treatments for insect bites and stings?
- Analgesics - relief of pain (acetaminophen, ASA, naproxen, ibuprofen)
- Oral antihistamines - relief of pain, itching, and inflammation of stings (1st and 2nd gen antihistamines)
What is the method of action of topical corticosteroids?
- Antipruritic and anti-inflammatory actions that can prevent or suppress dev’t of edema, capillary dilation, swelling and tenderness associated w/ inflammation
- Anti-inflammatory effects relieve pain and itching
What are the monitoring parameters for insect bites and stings?
- Pain/fever (up to 7 days)
- Itching - topical corticosteroids should relieve w/in minute; oral products w/in 1 hour
- Swelling/redness - should decrease w/in 24-48 hours
- Signs of infection
- Anaphylactic reaction - observe for first 30 minutes
